1. Field of the Invention
The field of the invention is that of handling flat articles to be placed in or removed from a cassette. This is particularly the case during the manufacture of integrated circuits, where silicon wafers are manipulated and positioned in cassettes and then are extracted from the cassettes to undergo other production operations.
Description of the Related Art
For the production of integrated circuits on silicon wafers, the control and handling of the wafers must take place from storage cassettes in which they are horizontally positioned. Each cassette has a series of racks constituted by lateral supports which can horizontally receive a series of wafers having identical dimensions. The handling of the wafers imposes the use of a system making it possible to take up a wafer stored in a cassette and then place the wafer in any random cassette on any random free rack.
In order to carry out these operations of gripping and putting back into place a wafer with respect to a cassette, it is known to use a gripping mechanism essentially constituted by a gripping finger able to remove a single wafer from the cassette and then to put it back into the latter. Due to the very limited height space separating two adjacent wafers, which is approximately 5 mm for the "SEMI-ENGINEERING" standard, the movements of the gripping finger must be very precise. Thus, any gripping system must be able to penetrate beneath the wafer to be removed without scratching the upper wafer. The height positioning of the gripping finger is ensured by a very precise, but onerous mechanical device, moving the finger and its support vertically. The gripping finger can also remain fixed, the precise vertical translation movement then being carried out by another mechanical device moving the cassette. In the latter case, it is the precision of the cassette translation mechanism which is very expensive.